Fig. 1.

Viability assay for cells containing an active dicentric chromosome. (A) Serial dilutions of WT and various COMA mutants were pronged on galactose (YPG), glucose (YPD), glucose + phleomycin (PHL), and glucose + hydroxyurea (HU) plates. Strains with a dicentric chromosome are indicated. Dilutions are twofold from Left to Right. Prong plates were repeated in triplicate with identical results. Individual plates and treatments are separated by spaces. (B) Quantitative analysis of cell viability expressed as a percent of single colony growth on galactose (inactive GALCEN). WT cells (J1781D) are not sensitive to low levels of PHL or HU. rad52Δ mutants exhibit reduced viability in the presence of PHL and HU. WT cells containing a dicentric chromosome exhibit reduced viability on YPD due to chromosome breakage. WT cells containing the dicentric chromosome are sensitized to PHL but not HU. Dicentric, rad52Δ viability is dramatically reduced on YPD, PHL, and HU. Dicentric, rad52Δ with mcm21Δ, iml3Δ, or chl4Δ exhibit increased viability on YPD relative to dicentric, rad52Δ cells, indicating suppression of dicentric breakage in these COMA mutants. Dicentric, rad52Δ with mcm21Δ, iml3Δ, or chl4Δ exhibit reduced viability relative to YPD in the presence of PHL and HU, indicative of chromosome breakage. Error bars are SEM. Student’s t-test values can be found in SI Appendix, Table S1. Dilution plating numbers can be found in SI Appendix, Table S2.